If a frequency at which a current is switched in an electric circuitry or a harmonic of this frequency matches an eigenfrequency of the electric circuitry, undesired oscillations of the current may be caused. These oscillations may reach a considerable amplitude. In commutating circuits, such oscillations may temporarily counteract a commutation and even generate over-voltages and over-currents which endanger the integrity of the parts of the commutating circuit. Further, electromagnetic fields irradiated by such oscillating currents may couple in other electronic parts and interfere with their function. Thus, reducing oscillations of currents, particularly of switched currents, occurring at a high frequency is often desirable. With many circuitries it is a requirement for their proper function.
A circuitry arrangement for reducing a tendency towards oscillations is known from DE 101 59 851 A1. This circuitry arrangement includes at least two semiconductor parts each comprising two terminals, one terminal of the one semiconductor part being electrically connected to one terminal of the other semiconductor part. Above this arrangement, at a distance to the two semiconductor parts, an eddy current attenuation structure is provided to attenuate oscillations which may occur during switching processes at a high frequency. The eddy current attenuation structure may be loop-shaped. The eddy current attenuation structure is not electrically connected to the semiconductor parts. The oscillations at a high frequency, however, generate eddy currents in the eddy current attenuation structure. The eddy current attenuation structure comprises a resistor resulting in ohmic losses of the eddy currents which attenuate the oscillations at the high frequency between the semiconductor parts. A sheet resistor of the preferably flat attenuation structure has to have a sufficiently high resistance to cause the ohmic losses of the induced eddy currents, but is has also to be small enough to allow for the generation of eddy currents. The resistance of the attenuation structure at which an optimum attenuation is provided shall be determined by measurements or simulations depending on the particular structure of the circuitry arrangement and the number of the semiconductor parts used. A simple adaptation of the attenuation structure to different semiconductor parts with which the circuitry arrangement is equipped, however, is not possible in this way.
A circuitry arrangement comprising electronic parts on an isolating substrate, magnetic materials being arranged in close vicinity to the electronic parts is known from DE 101 62 637 C1. The magnetic materials are galvanically separated from the electric circuitry arrangement but magnetically coupled thereto in such a way that electromagnetic resonances occurring at the electronic parts are attenuated. To have an effective coupling of the electromagnetic alternating field according to this principle, it is necessary to use magnetic materials, like for example ferromagnetic or ferrimagnetic materials, which have a high magnetic susceptibility. If the magnetic coupling between the alternating current and the magnetizable substance is successful, losses due to reversing the magnetization direction and due to magnetic hysteresis occur in the alternating field whose direction changes permanently. These losses are drawn from the source of the electromagnetic alternating field, i.e. from the resonant circuit, and thus attenuate the oscillations in the resonant circuit. Eddy currents in the magnetic materials shall be inhibited in the circuitry arrangement known from DE 101 62 637 C1.
A semiconductor module comprising a housing, a semiconductor element arranged in the housing and a framework is known from DE 101 23 232 A1. The framework comprises conductor tracks to which the semiconductor part is connected in an electrically conductive way. In the interior of the housing a casting compound is provided which is applied to the semiconductor part. The casting compound and/or the material of the housing are provided as attenuation materials with electromagnetically attenuating properties.
KR 100771146 B discloses a circuitry arrangement for suppressing switching oscillations and electromagnetic interferences at a high frequency. In this circuitry arrangement, a capacitor is provided between a conductor layer at power potential and a conductor layer at earth potential. The dielectric material of the capacitor comprises a high dielectric constant.
JP 2003101239 A also discloses a chip-capacitor for suppressing switching oscillations in a circuit board comprising several conductor layers. The chip capacitor is integrated in an isolation layer across which a power supply conductor and an earth conductor are facing each other.
US 2009/0296362 A1 discloses a multilayer printed circuit board having a plurality of wiring layers and an electronic component mounted thereon. Further, the circuit board includes a spiral EMI restriction wiring including a path in a substantial spiral shape configured with a printed wire section of a substantial loop shape provided along the circumference on each of at least two wiring layers. and a plug provided on each wiring layer arranged between a neighboring top wiring layer and a neighboring bottom wiring layer. A resistance element is inserted at some midpoint of the printed wire section at the outer surface of the circuit board. The resistance element converts energy of EMI coupled into the EMI restriction wiring into thermal energy.
US 2005/0068751A1 discloses a printed circuit board having a signal layer with signal traces, e. g. conductive paths, that electrically connect components, such as processors and integrated circuits, and one or more voltage planes, such as a power plane and a ground plane. For reducing electromagnetic resonance between voltage planes which may increase the impedance associated with a printed circuit board, one or more floating traces are provided on the signal layer. The floating traces are electrically conductive paths routed along the signal layer, that are electrically coupled to a voltage plane.
DE 103 33 806 A1 discloses a printed circuit board including at least one electronic component to be shielded and a shielding at least partially enclosing the electronic component. The shielding comprises a plane lid, a plane bottom and a wall element connecting the lid and the bottom.
There still is a need of a circuitry arrangement in which an attenuation of oscillations of a current flowing in operation of the circuitry arrangement can be optimized depending on the actual assembly of the circuit board with electronic parts.